DSS support for Adaptec MaxIQ™ SSD Cache solution

[SeanLeyne]

For the price of a MaxIQ setup (including SLC SSD), I don't get the benefit of a 32gb SSD cache over 32gb of RAM on the DSS machine.

To me, it seems like the only benefit of an SSD cache is that it persists across reboots. That's nice for a workstation, but it seems useless for a server.

RAM cache is certainly higher performance than SSD.

Remember that DSS doesn't provide any RAM cache for BLOCK IO LUNs/shares, only FILE IO, so in that case the SSD cache provided by MaxIQ would be extremely beneficial.

[rcohen]

Remember that DSS doesn't provide any RAM cache for BLOCK IO LUNs/shares, only FILE IO, so in that case the SSD cache provided by MaxIQ would be extremely beneficial.

Sure, if you disable caching on DSS, then you are totally relying on controller caching. Why would you want to do that?

All I can imagine is the possibility that the MaxIQ cache algorithm may be better for certain data access patterns. If that is truly happening in real-world applications, it seems like a better solution would be do have some more tunable settings on the DSS cache (size of MRU vs. MFU, etc.)

If the SSD cache provided more bang for the buck than RAM, that would be different, but that doesn't appear to be the case. Apparently, MLC SSDs aren't suitable for caching, due to performance and reliability issues with cache write patterns.

[SeanLeyne]

Sure, if you disable caching on DSS, then you are totally relying on controller caching. Why would you want to do that?

DDS does not do any caching of BLOCK IO LUNs/shares, period. There is nothing to disable.

[webguyz]

Only File I/O takes advantage of caching by using the extra memory on your motherboard, Block I/O just uses whatever cache you have on your disk controller but none on your motherboad. But you can't do autofailover if your doing File I/O.